The geographic idiosyncrasies of states and media markets set the stage for a natural experiment in which residents of a given state may be exposed to widely varying quantities of presidential television advertising. We use this natural experiment to estimate the effects of TV ads on voter turnout. Analysis of voting rates in media markets reveals that the volume of advertising purchased by the presidential campaigns during the final weeks of the 2000 election had negligible effects on voter turnout. Classifying presidential advertisements according to whether their tone is positive or negative, we find no evidence to suggest that attack ads promote or diminish turnout. Our findings stand in sharp contrast with recent survey-based studies that report strong turnout effects.